Wouldn't, then, have Scotty and the hapless redshirt in "Relics" also have been aware of the passage of time ...

Given Barkley's experiences, yes Scotty would have been aware of something, some passage of time. Now whether he was fully aware of 75 years of sharp personal perceptions, or instead a vague surreal existence in the recycling matter stream, is debatable.

Scotty was obviously confused for a half minute after materializing, one possibility is Scotty hallucinated in the matter stream limbo.

There is also the consideration that Scotty had a visible head injury, the laceration on his left forehead. This by itself could have been the cause of his confusion.